Moisture Absorption of Glass-Epoxy Sandwich Structure

The authors discuss the comparison of two types of E-glass/epoxy sandwich structures for multi-layer PWB (Printed Wiring Boards) in relation to moisture absorption. Moisture diffusion characteristics based on measuring the mass change of 1, 3, and 5 laminated layers were monitored at 40 degrees C within multiple humidity tests at humidity levels from 5% RH to 85 % RH. Based on the theoretically calculated time required for water absorption and desorption into epoxy samples filled with glass fibres, their absorption was experimentally confirmed depending on the thickness of the samples and also depending on the technology of their preparation (1 and 2 stage lamination of glass - epoxy laminated structure). From our experimental data, we obtained moisture saturation concentration at the humidity level from 5 % RH to 85% RH. The results of our analysis have shown that although epoxy constructions exhibit increased resistance to moisture penetration, it is not possible to completely prevent moisture inside these constructions. Ultimately, this should be taken into account when constructing packages with embedded components that cannot be considered to be hermetic. Our samples were exposed to 85 % moisture, while the moisture has been shown only in potential leaks among individual layers of pre-pregs sandwich, but also due to the saturation of the material itself, which is particularly activated along with the interface of samples. The results of the experiments can be used in creating multi-layer embedded sandwich structures, especially in terms of their reliability.